If you are going through a public hospital to have your baby (booked there) you will have all your scans done there and they are then free - in SA anyway but I know it is different in different States.

If you are going private with your own OB you will pay a fair bit (around $2000ish) for their fees, plus tests and ultrasounds. This will get added up towards your "Medicare Safety Net". Call Medicare or ask your Dr's receptionist about it. Basically you need to pay a certain amount (around $1000 from memory) and then costs above this are refunded at around 70%. It is calculated on the calendar year though so might not work out well for you - you could ask about paying some of the Dr fees early if you are going private to make sure they are in this calendar year. For us it has meant that we payed $250 per scan for the first four and then the next ones were only around $35, also got quite a few hundred back on OB's fees.

SO it depends on if you are going public or private and what state you live in. Ask Medicare and your Dr for help with sorting it out.